Field of the Invention
The present invention relates to a discharge device using discharge mainly by AC power which is used for, for example, fuel ignition in an internal-combustion engine.
Description of the Related Art
In recent years, problems of environmental conservation and fuel depletion are raised, and it is urgently necessary to take measures against these problems also in the automotive industry. As an example of these measures, there is a method of dramatically improving fuel consumption by reducing pumping loss (intake and exhaust loss) using EGR (Exhaust Gas Recirculation). However, the burnt gas as the exhaust gas is non-combustible and has a high heat capacity with respect to the air, therefore, there is a problem that ignitibility and combustibility are reduced when a large quantity of burnt gas is taken by the EGR.
As one of solutions for the problem, for example, in a corona discharge ignition system in JP-2014-513760A, a discharge method of igniting at multi-points and in a wide range using corona discharge to thereby form a stable flame kernel and to make combustibility be more stable. When using the disclosed ignition system, a more stable flame kernel can be formed as compared with a related-art ignition coil, and stable combustibility can be obtained, for example, when the large quantity of gas is inputted in the above EGR. Accordingly, a larger quantity of gas in the EGR can be inputted as compared with the related-art ignition system, and the pumping loss can be reduced, therefore, an internal-combustion engine capable of dramatically improving fuel consumption can be obtained.
In the related-art corona discharge ignition system of JP-2014-513760A, AC power is supplied to an ignition device 22 corresponding to an ignition plug as shown in FIG. 2. The electric current supplied to the ignition device 22 flows through a path of a high-voltage terminal 62 of a transformer 44, an inductor 27, the ignition device 22, a ground GND connecting to a current sensor 46, the current sensor 46 and the high-voltage terminal 62 of the transformer 44 in this order.
However, when the status of disconnection or connection failure occurs in the high-voltage terminal 62 of the transformer 44 in the corona discharge ignition system of JP-2014-513760A, there is a place where electrical capacitive coupling is made because a drive circuit 30 of the corona discharge ignition system is a device which outputs AC power. If there is a path for feeding back to a power generation source, AC current is outputted from the ignition device even when an original energizing path is disconnected, and the device is sometimes in a state as if it is normally operated. For example, the current may flow through a path of the high-voltage terminal 62 of the transformer 44, the inductor 27, the ignition device 22, the ground GND connecting to the current sensor 46, the current sensor 46, a low-pass filter 48, a square wave converter 50, an operational amplifier 38, a switch 42, a primary-side winding 66 of the transformer 44 and the high-voltage terminal 62 of the transformer 44 in this order.
In the case where a prescribed amount of current or more flows through the path, the operational amplifier, the switch or the like on the path may be damaged and the drive circuit may be broken, however, there is a case that an abnormality is not found just by observing a signal of the current sensor 46 as the drive circuit is operated in a near normal state.